body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Helvetica', 'Arial', sans-serif;
  margin: 0;
  padding: 0;
  color: #1d1d1f;
  background-color: #f5f5f7;
}

header {
  background-color: rgba(0, 0, 0, 0.8);
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 9999;
}

nav ul {
  list-style-type: none;
  padding: 0;
  margin: 0;
  display: flex;
  justify-content: center;
}

nav ul li {
  padding: 12px 20px;
}

nav ul li a {
  color: #f5f5f7;
  text-decoration: none;
  font-size: 14px;
}

main {
  padding-top: 44px;
}

section {
  padding: 100px 20px;
  text-align: center;
}

h1 {
  font-size: 56px;
  font-weight: 600;
}

h2 {
  font-size: 48px;
  font-weight: 600;
}

p {
  font-size: 21px;
  line-height: 1.5;
}

.avatar {
  width: 200px;
  height: 200px;
  border-radius: 50%;
  object-fit: cover;
}

footer {
  background-color: #f5f5f7;
  color: #86868b;
  text-align: center;
  padding: 20px;
  font-size: 12px;
}

@media (max-width: 768px) {
  h1 {
    font-size: 40px;
  }

  h2 {
    font-size: 32px;
  }

  p {
    font-size: 17px;
  }
}